1. Field of the Invention
The present invention relates to an image sensor incorporated into an electronic machine such as a facsimile machine, a printer, a copying machine or an optical character reader.
2. Description of the Related Art
An example of a conventional contact type (compact contact type) image sensor is shown in a side elevational view in FIG. 5. In this image sensor 160, a transparent cover (glass cover) 31 is attached to the upper portion of a frame 30, and a substrate 33 of a light projecting portion (a light emitting portion) having a light emitting device 32 is fixed to the frame 30 in such a manner as to be inclined toward the surface of the glass cover 31. A rod lens array (optical system) 34 for converging the light reflected from a copy (not shown) as the object being photographed is fixed to the frame 30 perpendicularly relative to the surface of the glass cover 31. A sensor substrate (substrate of a light receiving portion) 36 having a light receiving device 35 for receiving the light from the rod lens array 34 is disposed directly under the rod lens array 34. A hybrid substrate (substrate of a signal processing portion) 41 carrying an electronic part 40 for driving the light emitting device 32 and the light receiving device 35 and processing an image information signal is soldered to the upper surface of the sensor substrate 36.
Another example of a conventional contact type image sensor is shown in a side elevational view in FIG. 6. This image sensor 260 has fundamentally the same structure as the image sensor 160 shown in FIG. 5. A glass cover 51 is attached to the upper portion of a frame 50, and a substrate 53 of a light projecting portion having a light emitting device 52, a rod lens array 54 and a sensor substrate 56 having a light receiving device 55 are disposed in the frame 50. In this example, the substrate 53 of the light projecting portion is fixed to the frame 50 through an elastic piece 57. A hybrid substrate 11 carrying an electronic part 73 for processing a signal is electrically connected to the sensor substrate 56 by a lead frame which is soldered to the bottom surface of the sensor substrate 56.
In such an image sensor 160 (260), the light emitted from the light emitting device 32 (52) enters obliquely to the glass cover 31 (51) and it is projected onto the copy on the glass cover 31 (51). The light reflected from the copy perpendicularly relative to the glass cover 31 (51) is converged on the rod lens array 34 (54), and received and converted into an electric signal by the light receiving device 35 (55) .
In the image sensor 160 shown in FIG. 5, however, since the hybrid substrate 41 is soldered to the upper surface of the sensor substrate 36, it is often the case that flux or the like scatters on the light receiving device 35 during soldering and exerts deleterious influence on the light receiving device 35, which leads to the deterioration of the image quality. On the other hand, in the image sensor 260 shown in FIG. 6, although the light receiving device 55 is free from the deleterious influence of soldering, since the hybrid substrate 71 is situated under the sensor substrate 56, the substrates 56 and 71 together attain a great size and the height of the image sensor increases by the height of the hybrid substrate 71.